In Remington's Pharmaceutical Sciences, 14th Ed., p 1681, (1970), it is reported that pill coating has been a pharmaceutically accepted technique for well over ten centuries. For instance, Rhazes (850-932 A. D.) in the ninth century used a mucilage for coating pills, and Avicenna (980-1037 A. D.) is credited with the introduction of silver and gold pill coatings into medicine. At one time the coating of pills with finely powdered talcum, called pearl coating, was very popular. The gelatin coating of pills was introduced by Garot in 1838. The first sugar coated pills in the United States were imported from France in about 1842. The first sugar coated pills manufactured in the United States was in 1856 by Warner, a Philadelphia pharmacist. The coating of pills with tolu was done in about 1860 and twenty-four years later Unna introduced the enteric coated pill.
Various pharmaceutical articles of manufacture have been coated by the drug dispensing art. For example, tablets were coated to provide a more attractive dosage form, to protect the drug content from moisture and to enhance its taste. Then too, tablets were provided with a coat for releasing a drug by enteric dissolution in the intestine of a warm-blooded animal. Recently, in 1972, Theeuwes and Higuchi coated osmotic dosage forms with a semipermeable rate controlling wall for delivering a drug at a known rate per unit time.
While the above-mentioned dosage forms are useful in the management of health and disease serious disadvantages are associated with them. That is, usually organic solvents are used for applying the coating to the drug and serious, unwanted drawbacks accompany the use of organic solvents. For example, organic solvents generally are toxic to living tissue and they must be substantially pulled from the dosage form to avoid a hazard to the dosage form's recipient. Another serious drawback with the use of organic solvents is that they are flammable thereby possibly providing the danger of fire during the manufacturing process. Also, organic solvents present an environmental problem and the use of such solvents requires complicated recovery systems to avoid contaminating the environment. The recovery systems are expensive to operate and adds to the cost of the final dosage form.
It will be appreciated by those skilled in the drug dispensing art that if a coating is provided that is substantially free of organic solvents when coating drugs, drug granules, drug powders, drug dispensers, and the like, such a coating would have an immediate positive value and, concomitantly, represent an advancement in the drug coating art. Likewise, it will be appreciated by those versed in the dispensing art that if a coating that is applied from a non-organic solvent, and the coated delivery device possesses the thermodynamic ability to deliver a beneficial drug at a controlled rate, such a delivery device would have a practical application in the field of human and veterinary medicine.